There are a few misunderstandings here. You cannot change your IP address. IP addresses are leased to a modem (you can change your computer's local IP, which does nothing).

You cannot change your modem's MAC address. Well you can, but it is against federal law to do change anything within a modem. You can change your router's MAC address, which also does nothing. I once had a project to change an old modem's MAC address (which is against federal law by the way, so I wouldn't recommend it as any permanent solution). It requires work, as in opening the hardware and modifying the chipset via soldering. Didn't complete. Would like to get back to it someday.

Changing anything within your router does nothing, as the hardware setup goes Modem>Router>Computer, and DoS/DDoS attacks will hit your Modem first, therefore the packets are still being received, even if they are being rejected by the router.

Disconnecting your modem/router will not change IP address, as IP addresses are assigned and leased by an ISP to a modem.

In order to change your IP address, the only guaranteed way to change this is to switch ISPs. IP addresses work in blocks, and each block is owned by an IP company. Example (no accurate numbers, just an example):
IP address 100.0.0.0 though 102.255.255.255 is owned by Comcast
Ip address 11.0.90.0 though 11.0.255.255 is owned by Time Warner
Swapping ISPs will take you to a separate block, hence guaranteeing an IP address change.

Its possible that if you call your IP and tell them you can't connect, and get them to do a remote reset on your router that your IP address might change, but it also might not. You would have to try it out.

Technically, software like peerblock (www.peerblock.com) should deflect DDoS attacks (unconfirmed) in the same way a firewall would filter undesirable packets, however the packets will still be getting to you as they have to go though your modem first, and on top of that the way peerblock works they would have to be on one of the public block lists, otherwise peerblock would not block it. If you can intercept the IP addresses the packet bombings are coming from you can manually add those IP addresses into a peerblock blocking list.

The best thing you can do, is to use a VPN, or not let anyone get ahold of your IP address. If this means using a skype proxy, or not using skype at all, then so be it. I dont recall anything ever being wrong with vent back in the BC days, and steam voice chat seems to works just as well as skype, besides a mute button (not sure if IPs can be extracted via steam chat though).

Information comes from a DC operations engineer who deals with industrial level DDoS attacks on a very regular basis. The only way to effectively counter a DDoS attack at the industrial level is to obtain larger connections and hardware which costs tens of thousands of dollars.

There are a few misunderstandings here. You cannot change your IP address. IP addresses are leased to a modem (you can change your computer's local IP, which does nothing).

If your IP address is dynamic, and you have access to your router, it is in fact, very legal and possible to change your IP by changing the MAC address of your router and resetting your modem. You will be assigned a new, different IP based on the MAC address.

However, with the Skype resolvers people are using to obtain your IP address via your Skype username, changing your IP and making a new Skype may no longer be an effective method to stop being attacked by someone who has access to any Skype username you have stored on your machine.

If you are connected to the internet and have Skype installed on your machine, even if you are not logged on to that Skype username, Skype can be sending and/or receiving some data involving all usernames you have on your machine. We seem to have remedied this by deleting the old usernames from your machine when you create a new one prior to obtaining a new IP address. This is incredibly frustrating, as many of us have very large contact lists in order to enjoy the game at any given time, but so far it is the only way we have been able to stop attackers from just obtaining our new IP addresses.

To delete a Skype username from your machine:

Hold the Windows key and type r. In the box that comes up type %appdata%\Skype <enter>.

Find and delete any folder with the Skype name of an account you want to remove.

------ An alternative --------

An alternative to deleting your Skype username (thus holding onto the chat history) is to install Skype on a Flash USB drive. You could have two thumbdrives with two installations, one with your real Skype for when you don't need to avoid an attack and one that you use to create new Skypes to avoid ddos.

Before starting RBGs or a ladder climb (or games for fun as it's been lately), disconnect from the internet and Skype, remove the thumb drive with your real Skype installation. Insert your thumb drive with your other Skype installation, reset your IP and create a new Skype name on your alternative installation. I would make a new one every time you play with new people, and delete it from the thumb drive when you are done.